Continuous reforming regeneration process

ABSTRACT

A METHOD OF OPERATING A CONTINUOUS REFORMING-REGENEREATION PROCESS COMPRISING ONE OR MORE REFORMING REACTORS AND EMPLOYING A PLATINUM CATALYST WHEREIN CATALYST ACTIVITY IS MAINTAINED AT A PREDETERMINED LEVEL BY CONTINUOUS REGENERATION THEREOF WITHOUT THE REMOVAL OF ANY REACTOR FROM THE PROCESS STREAM.

p 1973 A. R. GREENWOOD ET AL 3,761,390

CONT INUOUS REFORMING -REGENERAT ION PROCES S Filed Oct. 19, 1971 k "3United States Patent Olfice 3,761,390 CONTINUOUS REFORMING-REGENERATIONPROCESS Arthur R. Greenwood, Niles, and Kenneth D. Vesely,

Arlington Heights, Ill., assignors to Universal Oil Products Company,Des Plaines, Ill.

Continuation-impart of application Ser. No. 860,905, Sept. 25, 1969, nowPatent No. 3,647,680. This application Oct. 19, 1971, Ser. No. 190,500The portion of the term of the patent subsequent to Mar. 7, 1989, hasbeen disclaimed Int. Cl. C10g 39/00 U.S. Cl. 208-65 19 Claims ABSTRACTOF THE DISCLOSURE A method of operating a continuousreforming-regeneration process comprising one or more reforming reactorsand employing a platinum catalyst wherein catalyst activity ismaintained at a predetermined level by continuous regeneration thereofwithout the removal of any reactor from the process stream.

This application is a continuation-in-part application of a copendingapplication Ser. No. 860,905 filed Sept. 25, 1969, now U.S. Pat. No.3,647,680.

The reforming of hydrocarbon feed stocks, such as a naphtha fractionderived from petroleum, utilizing a platinum group metal-aluminacatalyst, is a process well known in the art. Briefly, a naphtha feedstock is admixed with hydrogen and contacted with the catalyst, usuallyin a fixed bed reaction zone, at reforming conditions of temperature andpressure to cause at least a portion of a naphtha feed stock to beupgraded to products of improved octane value. Prior art reformingprocesses generally comprise one of two types of operation, i.e., anon-regenerative type and a regenerative type. In the practice of anon-regenerative type of operation, the catalyst is maintained incontinuous use over an extended period of time, say from about 5 monthsto about a year or more depending on the quality of the catalyst and thenature of the feed stock. Following this extended period of operation,the reforming reactor is taken off stream While the catalyst isregenerated or replaced with fresh catalyst. In the practice of theregenerative type of operation, the catalyst is regenerated with greaterfrequency utilizing a multiple fixed bed reactor system arranged forserial how of the feed stock in such a manner that at least one reactorcan be taken off stream while the catalyst is regenerated in situ orreplaced with fresh catalyst, one or more companion reactors remainingon stream, or going on stream, to replace the off stream reactor.Subsequently, the regenerated fixed bed reactor is placed on streamwhile another is taken off stream and the catalyst bed is regenerated orreplaced with fresh catalyst in like manner.

It is apparent from the brief description of prior art non-regenerativeand regenerative processes that both means of operation embody certainundesirable features. For example, in the non-regenerative type ofoperation, the entire plant is usually taken off stream to effectregeneration or replacement of the catalyst with a resultant significantloss in production. Further, the non-regenerative type of operation ischaracterized by a continuing decline in catalyst activity during theprocessing period requiring an operation of increasing severity tomaintain product quality, usually at the expense of product quantity. Inthe regenerative type of operation utilizing a multiple fixed bedreactor system, or swing reactor system, similar problems areencountered although to a lesser degree. However, the start up and shutdown Patented Sept. 25, 1973 procedures relating to insertion andremoval of a reactor in the process stream are unduly complicated andrequire a complex system of valves, lines and other equipment toaccomplish reactor change over with a minimum loss of process time.

It is therefore desirable to provide a reforming process which wouldsubstantially obviate the undesirable features of prior artnon-regenerative and regenerative type reforming processes. Morespecifically, it would be desirable to have a reforming process wherebya predetermined high level of catalyst activity and stability ismaintained without resorting to the removal of the reforming reactorfrom the process stream and a consequent loss of process time.

Accordingly, it is an object of this invention to present an improvedcatalytic reforming process whereby a predetermined high level ofcatalyst activity and stability is maintained over extended periods oftime. Thus, in accordance with one embodiment of this invention, thereis provided a method of operating a continuous reformingregenerationprocess employing a platinum group metal catalyst which comprisespreheating a hydrogen-hydrocarbon reaction mixture to reformingtemperature, charging the reaction mixture to a reactor and treating thereactant stream therein at reforming conditions in contact with anannular moving bed of catalyst particles moving as a substantiallyunbroken column through said reactor, with substantially lateral flow ofthe reactant stream therethrough; withdrawing used catalyst particlesfrom the said reactor while maintaining the same on stream at reformingconditions; passing the catalyst particles to a regenerator comprisingin a sequence a carbon burn-off zone, a halogenation zone and a dryingzone; moving said particles through said carbon burn-off zone, chargingan oxygen-containing gas thereto in contact with said particles andrecycling at least a portion of the resulting flue gases to said carbonburn-off zone to effect a controlled burning and removal of carbon fromsaid particles; passing the particles substantially free of carbon in asubstantially continuous moving bed through said halogenation zone incontact with steam admixed with a hydrogen halide in a mole ratio of atleast about 0.5 :1, and diluted with air to elfect halogen additionthereto; passing the halogenated particles in a substantially continuousmoving bed through said drying zone and drying said particles therein incontact with a stream of hot dry air; withdrawing catalyst particlesfrom said drying zone, treating the same in contact with hydrogen at atemperature of from about 800 to about 1200 F., and adding the reducedcatalyst particles to the catalyst contained in the aforesaid reactor toeffect a substantially constant catalyst inventory therein.

Another embodiment includes the above method wherein the catalystparticles from said drying zone and hydrogen are processed downwardly asa moving bed through a confined reduction zone in the upper portion ofthe reforming reactor to effect an indirect heat exchange relationshipwith the hot reaction mixture charged thereto whereby said catalystparticles are reduced in contact with hydrogen at a temperature of fromabout 800 to about 1200 F., the reduced catalyst particles beingprocessed downwardly and added to the moving catalyst bed contained insaid reactor to effect a substantially constant inventory therein.

Other objects and embodiments of this invention will become apparent inthe following detailed specification.

The catalyst employed in the practice of this invention comprises aplatinum group metal, combined halogen and alumina, the platinum groupmetal and combined halogen preferably being composited with a sphericalalumina such as prepared by the oil drop method described in U.S.

Pat. No. 2,620,314 issued to James Hoekstra. Preferably, the catalystwill comprise platinum and combined chlorine composited with alumina. Itis understood that the fatalyst may further include a promoter, such asrhenium, germanium, etc., as practiced in the art. Other platinum groupmetals including palladium, rhodium, ruthemum, osmium and iridium aresuitable although less commonly employed. Also, other refractoryinorganic oxides including silica, zirconia, boria, thoria, etc., aswell as com posites thereof such as silica-alumina, alumina-boria, andthe like, may be used with satisfactory results. Generally, the platinumgroup metal will comprise from about 0.01 to about 5.0 wt. percent ofthe catalyst composite, from about 0.10 to about 0.80 wt. percent beingpreferred. While the halogen component may be chlorine, bromine,fluorine and/or iodine, chlorine is most usually utilized to impart thedesired acid-acting character to the catalyst. The halogen componentsuitably comprising from about 0.50 to about 1.5 wt. percent of thecatalyst composite, is measured as elemental halogen although present ina combined form with one or more of the other catalyst components. Thoseskilled in the art are familiar with the preparation of the reformingcatalyst herein contemplated and, since the novelty of the presentinvention does not reside in the catalyst per se, a further detaileddescription is not warranted.

Catalytic reforming conditions include a temperature of from about 700to about 1000 F., a pressure of from about 50 to about 1000 p.s.i.g., aliquid hourly space velocity of from about 0.2 to about 10, and ahydrogen to hydrocarbon mole ratio of from about 1:1 to about 1. Themethod of this invention is particularly adapted to low pressurereforming, preferably at a pressure of from about 50 to about 200p.s.i.g. Since the reforming reaction is endothermic in nature, in theevent a multiple reactor system is employed, the eflluent from a givenreactor is generally reheated to reaction temperature prior tointroduction into the next succeeding reactor.

As used herein, the term activity relates to the capacity of thecatalyst system to convert the low octane naphtha feed stock to arelatively high octane product, for example, a gasoline fraction with anoctane rating in excess of about 90, at a given temperature, pressureand space velocity. The concept of the present invention permitsreforming of the hydrocarbon feed stock in contact with a catalystsystem characterized by a substantially constant activity level. This isaccomplished in part by the method of this invention which provides forthe constant replacement of used catalyst in the system with regeneratedcatalyst whereby the catalyst sysem remains at a substantially constantactivity level at a given temperature, pressure and space velocity. Thisis in contrast to conventional non-regenerative and regenerativeoperations where catalyst activity is maintained at a constant level byincreasing the severity of the operation.

In the schematic drawing, the reactant stream is depicted as beingprocessed through a multiple reactor system comprising two verticallystacked reactors with intermediate heating of the reactant streambetween reactors. However, it is understood that the reactant stream maybe processed through a multiple reactor system comprising reactorsarranged side-by-side in the common fashion and with intermediateheating of the reactant stream between reactors to maintain desiredreforming temperatures in the various reactors. It is further understoodthat a single reactor system may be employed, or any combination of thedescribed systems. In the multiple reactor system, fresh orreconditioned catalyst may be continuously added to an initial or topreactor and processed serially or sequentially through the reactorsystem, the catalyst being withdrawn from the final or bottom reactor,as the case may be, for reconditioning in accordance with the method ofthis invention. Alternatively, fresh or reconditioned catalyst may becontinuously added to each of two or more reactors, the catalyst beingwithdrawn from each of said reactors in incremental amounts forreconditioning according to the method of this invention. In the lattercase, the used catalyst from the various reactors is commingled in acommon hopper, regenerated according to the method of this invention,and subsequently distributed to said reactors as required to maintain asubstantially constant catalyst inventory therein. Alternatively, thecatalyst of a selected reactor may be periodically regenerated whilemaintaining all reactors of the system, including the selected reactor,on stream at reforming conditions.

In the preferred multiple reactor system comprising stacked reactors,the reactor system will in effect have a common catalyst bed moving as asubstantially unbroken column of particles from the top reactor to thebottom reactor. Thus, used catalyst is withdrawn from the bottom reactorwhile regenerated catalyst is added to the top reactor, and the catalystof the reactor system is regenerated with all reactors remaining onstream at reforming conditions.

Referring then to the drawing, and at the same time setting forth anillustrative operation, a straight-run gasoline fraction boiling in the200-400 F. range is charged to the process through line 1 and at aliquid hourly space velocity of about 2.0, entering a heater 2 inadmixture with a hydrogen-rich gas stream recycled through line 3 from aproduct separator not shown. In a conventional reforming operation, aconsiderable excess of hydrogen is admixed with the hydrocarbon chargeto minimize carbon formation on the catalyst. Typically, hydrogen isemployed in about a 10:1 mole ratio with the hydrocarbon charge.However, the method of this invention, wherein the catalyst is subjectedto frequent regeneration, affords a substantial reduction in hydrogenrecycle. Preferably, the hydrogen-hydrocarbon mole ratio is from about1:1 to about 5:1. Thus, in the present illustration, the heated combinedstream comprises hydrogen and hydrocarbon in a mole ratio of about 3:1,said heated combined stream being withdrawn from the heater 2 by way ofline 4 and charged into the upper portion of reforming reactor 5.

Reforming reactor 5 is shown in vertical alignment with reformingreactor 11, with an intermediate heater 10. The reforming catalystcharged to reactor 5, as hereinafter described, is comprised ofspherical ,3 diameter particles containing about 0.2 wt. percentrhenium, 0.375 wt. percent platinum and 0.9 wt. percent combinedchlorine, the remainder being alumina. The reactor temperatures aremaintained in the 850-950 F. range and the pressure at about 200p.s.i.g. Reforming reactor 5 is shown with catalyst confined in anannular moving bed 6 formed by spaced cylindrical screens 7. Thereactant stream is passed in an out-to-in radial flow through thecatalyst bed, the reactant stream continuing downwardly through thecylindrical space 8 formed by said annular bed 6 and exiting to heater10 by way of line 9. Since the reaction is endothermic, the effluentfrom the reactor 5 is reheated in heater 10 and thereafter charged toreactor 11 through line 12. Again, the reactants stream is passed in anout-toin radial fiow through the annular catalyst bed 13 substantiallyas described with respect to reactor 5, the flow passing downwardlythrough the cylindrical space 14 and passing from reactor 11 by way ofline 15. The reactor effluent withdrawn through line 15 is passed toconventional product separation facilities for recovery of high octaneproduct, for example, a reformate having a clear octane number rating ofabout 95, and recovery and recycle of a hydrogen-rich gas stream to thereactor system.

The catalyst particles descending through the reactor 5 as an annularmoving bed 6, are continued to the annular moving bed 13 of reactor 11by way of catalyst transfer conducits 16 and 17. Conduits 16 and 17represent a multitude of catalyst transfer conduits permitting passageof the catalyst between said annular beds 6 and 13 and effecting asuitable pressure drop whereby substantially all of the reactant streamfrom reactor is directed through the heater by way of line 9 with only aminimal amount by-passing said heater 10 and passing directly to reactor11 together with the catalyst flow through conduits 16 and 17. Thus, ineffect, the reactor system has a common catalyst bed moving as asubstantially unbroken column of particles through the top reactor 5 andthe bottom reactor 11. In the present example, the used catalyst iswithdrawn through lines 18 and 19 at a rate such that the catalystinventory of the reactor system is replaced in about 30 day cycles. Thecatalyst is withdrawn intermittently through line 20 and by means ofcontrol valve 21 to effect a moving bed type of operation, the catalystbeing discharged into a lock-hopper 22 for separation of residualhydrocarbon therefrom. The used catalyst is subsequently transferredthrough line 23 and control valve 24 to a lift engager 25 to be liftedin a nitrogen stream to a disengaging hopper 28 by way of line 27. Thecatalyst is litfed to said hopper 28 by a flow of nitrogen charged tothe lift engager 25 through line 26 from an external source not shown.Nitrogen is charged to the lift engager 25 at the rate of about 531standard cubic feet per hour and at a temperature of about 100 F.

The used catalyst deposited in the disengaging hopper 28 comprises about0.7 wt. percent combined chloride and 2-5 wt. percent carbon. Anoverhead line 29 is provided to vent the disengaging hopper 28 to theatmosphere or to recycle the nitrogen. Catalyst particles from thedisengaging hopper 28 are fed through line 30 to a catalyst regeneratorcomprising a carbon burn-off zone 31, a chlorination zone 32, and adrying zone 33. The catalyst particles are processed downwardly as amoving bed or column in a confined regeneration zone 34, passing fromthe carbon burn-off zone 31 to the chlorination zone 32. Chlorinated andsubstantially carbon-free particles are then continued downwardlythrough the drying zone 33 and contacted therein with a hot, dry airflow to effect the separation of excess adsorbed gaseous components fromthe catalyst.

In the present example, the catalyst particles are passed from thedisengaging hopper 28 to the catalyst regenerator at an average rate ofabout 200 pounds per hour. The catalyst particles are processeddownwardly through the carbon burn-off zone 31 at a rate to establish anaverage residence time therein of about 2 hours.

In the carbon burn-oft zone 31, the catalyst particles are heated incontact with an oxygen-containing gas including hot recycle gasescharged to the carbon burn-off zone 31 at a gaseous hourly spacevelocity of about 4700 by way of line 44. The oxygen-containing gas isderived from air charged to the drying zone 33 by way of line 35, theair becoming admixed with steam, chlorine, and HCl on passing upwardlythrough the chlorination zone 32, and the gaseous mixture continuingupwardly through the carbon burn-off zone 31 in contact with thecatalyst particles contained therein. The resulting gaseous products,including oxides of carbon and sulfur, are withdrawn from the carbonburn-off zone 31 as flue gases through line 36. In some cases, it may bedesirable to separate sulfur components from the flue gases prior torecycle. In that event, the flue gases are charged to a scrubber 37wherein they are admixed with a caustic stream recycled from a causticsettling tank 40 through a cooler 65 and line 38. The mixture is thenpassed to the caustic settling tank via line 39. The resulting fluegases, substantially free of halogen and oxides of sulfur, are recoveredoverhead from the settling tank 40 through line 41 and charged by meansof a blower 42 through a heater 43 and line 44 to the carbon burn-offzone 31 as aforesaid. The heater 43 is provided for start-up operation.The gases recycled to the carbon burn-off zone 31 comprise about 0.7 wt.percent oxygen to effect a controlled burning at a temperature of fromabout 830 to about 930 F. in the burn-off zone. An overhead vent line 45is provided to discharge excess flue gas from the process.

The catalyst particles, substantially free of carbon, are passed througha halogenation zone in contact with steam admixed with a halogen, orsuitably a hydrogen halide, in a mole ratio of at least about 0.5: 1.Pursuant to the process of this invention, the catalyst particles arepassed through a halogenation zone in contact with steam admixed with ahydrogen halide in a mole ratio of at least about 0.5 :1, and in therange of from about 0.5:1 to about :1. It is understood that saidhydrogen halide may be formed in situ in said halogenation zone, forexample by charging steam admixed with t-butylchloride, or othercompound hydrolyzable to a hydrogen halide at treating conditions, tosaid halogenation zone to provide a steam-hydrogen halide mole ratiotherein of at least about 0.5: 1.

In the present illustrative example, the catalyst particles,substantially free of carbon are processed downwardly from the carbonburn-off zone 31 through a chlorination zone 32 at conditions to effectan average residence time therein of about 1 hour. In the chlorinationzone 32, the catalyst particles are brought in contact with about a 2:1mole ratio of steam and hydrogen chloride being admixed with air passingupwardly from the drying zone 33 as previously mentioned. Steam ischarged to the system at a temperature of about 450 F. and at a rate ofabout 2.4 pounds per hour through line 47. The steam is passed throughline 50 together with recycle vapors contained therein and admixed withhydrogen chloride from line 48, the hydrogen chloride being charged at arate of about 1.45 pounds per hour. The steam-hydrogen chloride mixtureis heated to a temperature of from about 750 to about 1100 F., and inthe present example to about 930 F., in heater 49 and charged to thechlorination zone 32 through line 46 at a gaseous hourly space velocityof about 4700. A recycle stream comprising excess steam and hydrogenchloride is withdrawn from the chlorination zone 32 by way of line 50and circulated by means of a blower 51 as a portion of thesteam-hydrogen chloride charged to the chlorination zone 32.

From the chlorination zone 32, the catalyst particles are continueddownwardly through the drying zone 33 whereby vaporous components arestripped from the catalyst by a flow of dry air. The air is charged tothe system through line 52 from an external source not shown and heatedto 750-1150 F. in heater 53 prior to being charged to the drying zone 33through line 35. The air is charged at a gaseous hourly space velocityof about 150.

The catalyst particles are withdrawn from the regenerator at regularintervals by way of line 54 through control valve 55 and collected inlock-hopper 56. The catalyst is subsequently transferred to a liftengager 57 through line 58 and control valve 64 to be conveyed to thereforming reactor 5. The catalyst particles are carried through line 60by a dry, pure hydrogen stream introduced to the lift engager 57 by wayof line 59 at about 3300 standard cubic feet per hour and at atemperature of about ambient. The hydrogen is subsequently used as areducing gas and as a portion of the hydrogen feed to the reformingreactor 5.

Prior to direct contact with the reactant stream in reforming reactor 5,the catalyst, in admixture with hydrogen, is processed in a dense phasethrough a reducing zone 61 to effect an indirect heat exchange with hotreaction gases charged to said reactor. The catalyst is processeddownwardly through the reduction zone 61 at a rate to establish aresidence time of about 2 hours therein at a temperature of 950l000 F.The resulting reduced catalyst is thereafter added to the catalyst bedthrough lines 62 and 63 replacing that withdrawn from the reactor systemthrough lines 18 and 19 for regeneration.

The method of this invention finds particular application with respectto low pressure reforming. While low hydrogen partial pressures favorthe main octane-improving reactions, e.g., dehydrogenation of paraffinsand naphthenes, a principal objection to low pressure reforming is inthe excessive formation of carbon resulting from condensation andpolymerization reactions also favored by low hydrogen partial pressures.However, the continuous reforming-regeneration process of this inventionsubstantially obviates this objection, and the relative catalystinstability reulting from carbon formation is no longer a limitingfactor to a successful low pressure reforming operation.

An added advantage derived from the practice of this invention is in theincreased and continued supply of hydrogen available forhydrogen-consuming refinery operations, such as hydrocracking.

We claim as our invention:

1. A method of operating a continuous reformingregeneration processemploying a platinum group metal catalyst which comprises:

(a) preheating a hydrogen-hydrocarbon reaction mix ture to reformingtemperature, charging the reaction mixture to a reactor, and treatingthe reactant stream therein at reforming conditions in contact with anannular moving bed of catalyst particles moving as a substantiallyunbroken column through said reactor, with a substantially lateral flowof the reactant stream therethrough;

(b) withdrawing used catalyst particles from said reactor whilemaintaining the same on stream at reforming conditions;

(c) passing the catalyst particles to a regenerator comprising insequence a carbon burn-off zone, a halogenation zone and a drying zone;

((1) moving said particles through said carbon burnoff zone, charging anoxygen-containing gas thereto in contact with said particles andrecycling at least a portion of the resulting flue gases to said carbonburn-off zone to effect a controlled burning and removal of carbon fromsaid particles;

(e) passing the particle substantially free of carbon in a substantiallycontinuous moving bed through said halogenation zone in contact withsteam admixed with a hydrogen halide in a mole ratio of at least about0.5 :1 and diluted with air to effect halogen addition thereto;

(f) passing the halogenated particles in a substantially continuousmoving bed through said drying zone and drying said particles therein incontact with a stream of hot dry air;

(8) withdrawing catalyst particles from said drying zone, treating thesame in contact with hydrogen at a temperature of from about 800 toabout 1200 F., and adding the resulting reduced catalyst particles tothe catalyst contained in the aforesaid reactor to effect asubstantially constant catalyst inventory therein.

2. The method of claim 1 further characterized in that said carbonburn-off zone is maintained at a temperature of from about 750 to about1100 F.

3. The method of claim 1 further characterized in that said reformingconditions include a temperature of from about 700 to about 1000 F., apressure of from about 50 to about 200 p.s.i.g., a liquid hourly spacevelocity of from about 0.2 to about 10, and a hydrogen to hydrocarbonmole ratio of from about 1:1 to about 10:1.

4. The method of claim 1 further characterized with respect to step (d)in that said flue gas recycled to said carbon burn-off zone comprisesfrom about 0.5 to about 1.5 mole percent oxygen.

5. The method of claim 1 further characterized with respect to step (d)in that said flue gas is recycled to said carbon burn-off zone through ascrubbing means to effect the separation of S0 and other sulfurcomponents contained therein.

6. The method of claim 1 further characterized in that said halogenationzone is maintained at a temperature of from about 750 to about 1100 F.

7.. The method of claim 1 further characterized with respect to step (e)in that said steam is admixed with hydrogen chloride in a mole ratio ofat least about 0.5:1.

8. The method of claim 1 further characterized in that said drying zoneis maintained at a temperature of from about 750 to about 1150 F.

9. The method of claim 1 further characterized with respect to step (g)in that said catalyst particles from said drying zone and hydrogen areprocessed downwardly as a moving bed through a confined reducing zone inthe upper portion of said reactor to effect an indirect heat exhangerelationship with the hot reaction mixture charged thereto whereby saidcatalyst particles are reduced in contact with hydrogen at a temperatureof from about 800 to about 1200" F., the reduced particles beingprocessed downwardly and added to the moving catalyst bed of saidreactor to effect a substantially constant inventory in said reactor.

1.0. A method of operating a continuous reforming regeneration processemploying a platinum group metal catalyst which comprises:

(a) preheating a hydrogen-hydrocarbon reaction mixture to reformingtemperature and charging the same to a multiple reactor systemcomprising stacked reactors openly connected through a catalyst transferconduit, each reactor containing a moving bed of catalyst particlesdisposed therein; moving said particles downwardly from the moving bedof an upper reactor to the moving bed of a next lower reactor throughsaid catalyst transfer conduit whereby a pressure drop is created acrosssaid conduit and the reactant stream passing downwardly through theupper reactor in contact with the catalyst contained therein is directedto a reactor outlet provided therefore; passing the reactant stream fromsaid upper reactor through a heating means, and charging the reheatedstream to the next lower reactor in contact with the moving bed ofcatalyst particles contained therein;

(b) withdrawing used catalyst particles from the bottom reactor whilemaintaining all reactors on stream at reforming conditions;

(c) passing the catalyst particles to a regenerator comprising insequence a carbon burn-off zone, a halo-- genation zone and a dryingzone;

(d) moving said particles through said carbon burnoff zone, charging anoxygen-containing gas thereto in contact with said particles andrecycling at least a portion of the resulting flue gases to said carbonburn-off zone to effect a controlled burning and removal of carbon fromsaid particles;

(e) passing the particles substantially free of carbon in asubstantially continuous moving bed through said halogenation zone incontact with steam admixed with a hydrogen halide in a mole ratio of atleast about 1:1 and diluted with air to effect halogen addition thereto;

(f) passing the halogenated particles in a substantially continuousmoving bed through said drying zone and drying said particles therein incontact with a stream of hot dry air;

(g) withdrawing catalyst particles from said drying zone, treating thesame in contact with hydrogen at a temperature of from about 800 toabout 1200 F., and adding the resulting reduced catalyst particles tothe catalyst contained in the aforesaid stacked reactor system to effecta substantially constant catalyst inventory therein.

11. A method of claim 10 further characterized in that said carbonburn-off zone is maintained at a temperature of from about 750 to about1100 F.

12. The method of claim 10 further characterized in that said reformingconditions include a temperature of from about 700 to about 1000" R, apressure of from about 50 to about 200 p.s.i.g., a liquid hourly spacevelocity of from about .2 to about 10, and a hydrogen to hydrocarbonmole ratio of from about 1:1 to about 10:1.

13. The method of claim 10 further characterized with respect to step(a) in that said stacked reactors contain said catalyst in an annularmoving bed, moving as a substantially unbroken column of particlesthrough said reactors, with a substantially lateral How of the reactantstream therethrough.

14. The method of claim 10 further characterized with respect to step(d) in that said fine gas recycled to said carbon burn-01f zonecomprises from about 0.1 to about 1.5 mole percent oxygen.

15. The method of claim 10 further characterized with respect to step(d) in that said flue gas is recycled to said carbon burn-off zonethrough a scrubbing means to effeet the separation of S and other sulfurcomponents contained therein.

1.6. The method of claim further characterized in that said halogenationzone is maintained at a temperature of from about 750 to about 1100 F.

17. The method of claim 10 further characterized with respect to step(e) in that said steam is admixed with hydrogen chloride in a mole ratioof at least about 0.5: 1.

18. The method of claim 11 further characterized in that said dryingzone is maintained at a temperture of from about 750 to about 1150 F.

19. The method of claim 10 further characterized with respect to step(g) in that said catalyst particles from said drying zone are chargedtogether with hydrogen to the top reactor of said stacked reactor systemand processed downwardly as a moving bed through a confined reducingzone in the upper portion of said reactor to effect an indirect heatexchange relationship with the hot reaction mixture charged to the upperportion thereof whereby said catalyst particles are reduced in contactwith hydrogen at a temperature of from about 800 to about 1200 F., thereduced particles being processed downwardly and added to the movingcatalyst bed of said reactor to efiect a substantially constant catalystinventory in said reactor system.

References Cited UNITED STATES PATENTS 3,647,680 3/ 1972 Greenwood eta1. 208- 2,689,821 9/1954 Inhoff et a1 208-175 2,854,405 9/ 1958Bergstrom 208-175 3,003,948 9/1961 Evans 208-65 3,132,092 5/1964 Vaell208-175 2,856,350 10/1958 Love 208- 2,856,351 10/1958 Welty et a1.208-140 3,117,076 1/ 1964 Brennan et al. 208-140 3,134,732 5/ 1965Kearby et a1. 208-140 3,375,190 3/1968 McHenry et a1 208-140 DELBERT E.GANTZ, Primary Examiner J. W. HELLWEGE, Assistant Examiner US. Cl. X.R.

